Firefighters, emergency response personnel, members of the military, racing personnel, and industrial workers that can be exposed to flames, high temperatures, and/or electrical arcs and the like, need protective clothing and articles made from thermally resistant fabrics. Any increase in the effectiveness of these protective articles, or any increase in the comfort or durability of these articles while maintaining protection performance, is welcomed.
A fiber known as polysulfonamide fiber (PSA) is made from a poly (sulfone-amide) polymer and has good thermal resistance due to its aromatic content and also has a low modulus, which imparts flexibility to fabrics made from the fiber; however, the fiber tends to shrink when exposed to a high heat flux such as a flame. Such high fiber shrinkage provides less thermal protection when used in protective garments, because fabrics made from such fibers tend to break open when exposed to high heat fluxes or flames, resulting in higher burn injures to the protective garment wearer. Therefore what is needed is a way of incorporating PSA into yarns for use in protective fabrics, garments, and apparel that utilizes the benefits of the PSA fiber while compensating the deficiency of the fiber.